This invention relays generally to a retinal display.
A retinal display is a display that is scanned directly into the eye of the user. An image for display may be raster scanned by scanning a light source directly into the retina of the user. A color gamut formed of red, green and blue (RGB) (or other available color spaces) may be implemented using appropriate light sources. Each light source may be a laser, laser diode or light emitting diode as examples.
A scanner scans the light source, one (or more) pixel at a time, directly onto the user""s retina. A horizontal scanner may use a flexure based mechanical resonance scanner that operates at several kilohertz. A vertical scanner may also be a mechanical scanner operated at non-resonant mode at the frame rate of the display. Other scanners may be utilized as well.
Microvision Inc. of Seattle, Wash. has developed a virtual retinal display 30 that includes a plurality of modules as shown in FIG. 6. The drive electronics module 34 receives and processes signals from an image or graphics source 32. These signals may contain information to control the intensity and color coordinates of a pixel that comprises a part of an image. The drive electronics 34 synchronize the data source with the scanning position information obtained from sensors. The drive electronics 34 in turn communicate with a photonics module 36.
The photonics module 36 may include light sources 38, modulators 42, and color combining optics 40. The display 30 may use very low power light sources 38 to create an image, a single pixel at a time. Gray levels may be created by changing the luminance on a pixel-by-pixel basis. A modulator 42 may take a pixel voltage from a video processor. Laser diodes may be modulated directly by changing the drive current. For laser-based systems, acousto-optic modulators may be used to modulate the beam.
Next, a scanner module 46 that may be mounted on a pair of eye glasses 48, provides mechanical horizontal and vertical scanning to project one pixel at a time onto a diffuser 54. That image may then be transferred through the optics to the retina of a person wearing the glasses 48. By rapidly moving the light source across and down the retina, an image may be painted in a raster pattern. A mechanical resonance scanner may sweep the horizontal axis and a non-resonance scanner may sweep the vertical axis. Eventually, micro-electromechanical scanners (MEMS) that are smaller and lighter than mechanical resonance scanners may be used.
As shown in FIG. 6, the scanner module 46 may include the scanners 52, a focusing lens 50 and a folding mirror 52. In scanning retinal display systems, the display exit pupil may be located at the eye-pupil of the observer. Refractive, reflective and diffractive optical elements can be used to expand and transmit the scanning beam of light through the user""s pupil and onto the retina to create the viewable image. Magnification, scan angle, and scanning mirror size determine the field of view and exit pupil size. Since scanning systems may create an exit pupil that is relatively small, a diffractive optical system with a forward scattering diffuser may be used at the intermediate image plane.
The use of a plurality of modules facilitates the design and development of the display. However, it also increases the size and weight of the system and complicates interconnectivity. In some cases the system may not be amenable to head-mounted display or integratable into a handheld portable device such as a Cell Phone or PDA.
Thus, there is a need for better ways to implement retinal displays.